SOLVED Softii - first build... no sound 🙃

[Petethefuzz]

Hi guys. Total n00b here. Just finished my first build. Maybe I took on to much, but I fell in love with the SFT so I wanted a clone. With help online/facebook I have tested that the switch works (multimeter buzz test). LED works. I’m very new
to electronics/circuits and even the multimeter. I have seen this kit in the forum - has anyone had the same issue? Doesn’t work out of the enclosure either, so it doesn’t appear to be pots making a short or something like that. I had to wire one of the transistors cause the socket
Was broken. I bought it as a kid from musikding.de

If you would be so kind to give me instructions on what and how to test, maybe with the multimeter, I’d really appreciate it. Please feel free to address me as a total beginner. If you feel like you are writing to a toddler your probably doing great

 

[peccary]

Just reflowed everything. Still no luck. Will cleaning the board potentially fix anything or just make it easier to check out? I’ve used the multimeter on the resistors and I think they check out fine. Anything else I can check?

You could potentially have bits of solder or snipped leads that are stuck in the flux that are making a connection somewhere. I think that might be a long shot, but it is possible. It will make it a lot easier to see what's going on, though. I was reading a thread yesterday where someone had a cut in the PCB that was preventing things from working properly, and having a clean board would make things like that much easier to see.

If you get a shallow dish and fill it with iso you can sit it in there with the pots sticking above the liquid. Getting iso in the pots won't kill them or anything but it'll probably wash away whatever they use to lubricate pots. You don't have to be paranoid about soaking the board, I guess, is what I'm saying.

Speaking as someone who had little to no electronics experience it was a trip for me to soak a populated board in alcohol, but I now have a little bag that I put finished boards in (before installing pots and switches) with iso and agitate it for a few minutes, then scrub with a toothbrush, then agitate again, and then use compressed air to dry. Just make sure all of the iso has evaporated before powering it up, which shouldn't take long. Compressed air and Kim Wipes (or even paper towels) will make things easier.

 

[BuddytheReow]

If you've got alligator clips I would suggest building a test probe and testing the signal at the trannies first. Google it, but you'll need a 100nf capacitor as well. Clip one end into a spare jack (not the ground point) and the other one of the legs of the capacitor. Free capacitor lead is your probe. Use another aligator clip to ground the jack. You can clip the end of that one to the ground of the guitar jack. You wont get signal one of the legs most likely (need to double check the schematic).

 

[TSReppe]

If you've got alligator clips I would suggest building a test probe and testing the signal at the trannies first. Google it, but you'll need a 100nf capacitor as well. Clip one end into a spare jack (not the ground point) and the other one of the legs of the capacitor. Free capacitor lead is your probe. Use another aligator clip to ground the jack. You can clip the end of that one to the ground of the guitar jack. You wont get signal one of the legs most likely (need to double check the schematic).

Yeah an audio probe would be my next move here. Just follow the schematic point by point till you find out where the problem is.

 

[Petethefuzz]

Hi guys! Thank you for the help so far. I’ll clean the board next week and order the parts needed to build an audio probe. Might take some time to arrive so I hope you will help me when I’m ready to probe the damn thing

 

[Chuck D. Bones]

We'll be here! When you're ready, I can recommend some points to probe. We're gonna fix this thing.

 

[Petethefuzz]

Ok so stuff came today and I made this, really rough, probe . Lot of hum but I can get music from my phone to pass when holding ground wire. The signal goes as far as R21 which should be the last in the circuit right? I’ve probed R21, 23,9,2,22 and 19 all with signal passing as I thought it would be smart to check after each pot. Does it make sense?

- or just forget everything above and feel free to point me in the right direction

I still need to do the cleaning as well...

 

[Petethefuzz]

 

[fig]

Q1 - good
Q2 - not good recheck this one
Q3 - good
Q4 - good
Q5 - bad connection? lead(s) may be loose in the socket.
Q6 - good

That funk on the board is flux residue. The solder is hollow and has resin in the middle to act as a cleaner and a glue. Was the board with alcohol.

Q2 is also the only one not socketed...was there an issue soldering this? It may have gotten too hot.

 

[BuddytheReow]

Check the signal on the trannies. In general, one leg should have no sound, one leg should be the "in" signal, and the "out" signal should be louder and/or more distorted.

 

[Petethefuzz]

Q2 is also the only one not socketed...was there an issue soldering this? It may have gotten too hot.

The socket was broken so I had to solder it. I’ll probe it again thanks.

 

[Petethefuzz]

Check the signal on the trannies. In general, one leg should have no sound, one leg should be the "in" signal, and the "out" signal should be louder and/or more distorted.

Thanks I’ll do that! What about if I probe the input jack lug -if pedal is engaged should it then work on both sleve and tip?

 

[fig]

Sorry, just read where you already mentioned the Q2 socketing. I somehow missed that in the thread. Carry on!

 

[BuddytheReow]

Thanks I’ll do that! What about if I probe the input jack lug -if pedal is engaged should it then work on both sleve and tip?

Sleeve is ground, so no sound will come out of there. You will have sound on the input jack regardless if pedal is engaged or not.

 

[BuddytheReow]

I think, and I could be wrong and hope someone corrects me, this is how the signal goes through the pedal. As I mentioned, probe each of the trannies. You probably won't get any signal on pin 2 since they are grounded. Personally I would start at the beginning and move forward. Once you get to a transistor with no signal, you can narrow down the area where the problem might be.

I should have asked this before: did you check the pinout of all your transistors before installing? If they aren't in the right way, the pedal won't work.

 

[Chuck D. Bones]

Yeah, pretty much like that.

Did you ever get a good voltage reading on Q2-S with no signal? It should be about the same as Q4-S and Q6-S.

Are you able to get a stable voltage reading on Q5-S?

Until we get those straightened out, there is no point in audio probing.

 

[andrew]

Q1 - good
Q2 - not good recheck this one

Regarding transistor voltages, how do we know what to be looking for? Is it specific to transistor model (and therefore findable in product documents)? Determined by the circuit, somehow?

 

[Chuck D. Bones]

The short answer: circuit analysis. I study the schematic and consult the data sheets. For the simpler circuits, like this one, I do a few calculations. With more complicated circuits, running a simulation is the better option. Not a simple process unless you've done it many, many times.

 

[Petethefuzz]

Did new reading. This time powering the pedal by battery.
Q1 1,28
Q2 9,3
Q3 0,81
Q4 5,95
Q5 0,84 (Stable)
Q6 5,43

Does this point towards a problem with Q2 or maybe components around it?

 

[fig]

Does this point towards a problem with Q2 or maybe components around it?

nope...it's definitely cursed.

 

[Petethefuzz]

nope...it's definitely cursed.

Is that pedal builder lingo for “not working”?